Chemistry:Metacresol purple

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Metacresol purple
M-cresol purple.svg
Identifiers
3D model (JSmol)
ChemSpider
UNII
Properties
C21H18O5S
Molar mass 382.43 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Metacresol purple or m-cresol purple, also called m-cresolsulfonphthalein, is a triarylmethane dye and a pH indicator. It is used as a capnographic indicator for detecting detect end-tidal carbon dioxide to ensure successful tracheal intubation in an emergency.[1][2] It can be used to measure the pH in subzero temperatures of saline or hypersaline media.[3]

In colorimetric capnography, the indicator is incorporated in an aqueous matrix that provides a pH just above the indicator's colour change.[4] When exposed to carbon dioxide (CO2), it undergoes a colour change from purple to yellow, because when CO2 dissolves in the matrix, it forms carbonic acid.[5]

In chemistry, it has two useful indicator ranges:[2]

  • pH 1.2–2.8: red to yellow
  • pH 7.4–9.0: yellow to purple

See also

References

  1. "Capnography" (in en-US). LITFL • Life in the Fast Lane Medical Blog. https://lifeinthefastlane.com/ccc/capnography/. 
  2. 2.0 2.1 "m-Cresol Purple 857890". https://www.sigmaaldrich.com/catalog/product/sial/857890. 
  3. Loucaides, Socratis; Rèrolle, Victoire M. C; Papadimitriou, Stathys; Kennedy, Hilary; Mowlem, Matthew C; Dickson, Andrew G; Gledhill, Martha; Achterberg, Eric P (2017). "Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures". Scientific Reports 7 (1): 2481. doi:10.1038/s41598-017-02624-0. PMID 28559544. Bibcode2017NatSR...7.2481L. 
  4. Gedeon, A.; Krill, P.; Mebius, C. (1994-09-01). "A new colorimetric breath indicator (Colibri)" (in en). Anaesthesia 49 (9): 798–803. doi:10.1111/j.1365-2044.1994.tb04457.x. ISSN 1365-2044. PMID 7978140. 
  5. Hagberg, Carin A. (2007-02-23) (in en). Benumof's Airway Management. Elsevier Health Sciences. ISBN 978-0323070171. https://books.google.com/books?id=aMEVmdRpU0IC&q=Metacresol+purple+changes+from+purple+to+gold+with+CO2.&pg=PA1062. 
Metacresol purple (pH indicator)
below pH 7.4 above pH 9.0
7.4 9.0
Metacresol purple (pH indicator)
below pH 1.2 above pH 2.8
1.2 2.8